from the official guide (12th edition)
A marketing firm determined that, of 200 households surveyed, 80 used neither Brand A nor Brand B soap, 60 used only Brand A soap, and for every household that used both brands of soap, 3 used only Brand B soap. How many of the 200 households surveyed used both brands of soap?
(A) 15
(B) 20
(C) 30
(D) 40
(E) 45
the answer is A. i know how to get it by doing simple arithmetic and algebratic calculations.
but i wonder if there's a quicker, efficient way to answer this.
i learned of an overlapping set formula. total = group 1 + group 2 - Both + Neither.
i tried to use that formula on this question and i couldn't figure it out.
so my assumption is the formula can be used for most overlapping set questions, but not all including this one.
am i correct?
A marketing firm determined that, of 200 households surveyed, 80 used neither Brand A nor Brand B soap, 60 used only Brand A soap, and for every household that used both brands of soap, 3 used only Brand B soap. How many of the 200 households surveyed used both brands of soap?
(A) 15
(B) 20
(C) 30
(D) 40
(E) 45
the answer is A. i know how to get it by doing simple arithmetic and algebratic calculations.
but i wonder if there's a quicker, efficient way to answer this.
i learned of an overlapping set formula. total = group 1 + group 2 - Both + Neither.
i tried to use that formula on this question and i couldn't figure it out.
so my assumption is the formula can be used for most overlapping set questions, but not all including this one.
am i correct?
